A fuel pellet and a manufacturing method thereof

Abstract

A fuel pellet and a manufacturing method thereof are disclosed. The method includes S1) weighing raw materials including 0-2% of chromium trioxide, 0-2% of alumina, 0-2% of silicon oxide and 0-2% of niobium pentoxide, with the balance being uranium dioxide; S2) ball milling and fully mixing the raw materials to form a powder mixture; S3) compressing the powder mixture to form a uranium dioxide blank, and subjecting the blank to high-temperature pre-sintering; S4) crushing the blank, sieving the crushed blank, and grinding the crushed blank into uranium dioxide particles; S5) adding beryllium oxide powder into the uranium dioxide particles, mixing the mixture to form powder to be compressed, with each uranium dioxide particle being covered with a cover layer formed from the beryllium oxidepowder; and S6) subjecting the powder to be compressed to compression molding and densification sintering to obtain the fuel pellet. A manner of two times of compound addition and two times of sintering is adopted, and therefore sintering aids form solid solution or are distributed in the uranium dioxide matrix, diffusion or solid solution formation of the sintering aids into the beryllium oxide is reduced, and on the premise that the sintering aids do not influence heat conductivity of the BeO phase, the pellet crystal grain size is effectively increased, and sintering activity is improved.

Description

technical field [0001] The invention relates to the technical field of nuclear fuel elements, in particular to a fuel pellet and a manufacturing method thereof. Background technique [0002] Thanks to UO 2 With the advantages of high melting point, good stability, and good radiation performance, most of the fuel elements of commercial nuclear reactors in the world use UO 2 as fuel pellets. However, UO 2 The thermal conductivity of ceramics is low, and the fuel pellets form a large temperature gradient during service, and the core temperature reaches above 1500 °C. A large temperature gradient leads to thermal stress in the pellets, and a high temperature of the pellets increases the release rate of fission gases, which is not conducive to the increase in the burnup of fuel elements and affects the safety and economy of nuclear power. [0003] In order to reduce the thermal stress of pellets and reduce the release rate of fission gas, adding second-phase compounds with hi...

AI Technical Summary

Problems solved by technology

However, the uniform and continuous distribution in UO 2 The BeO in the matrix inhibits the diffusion of ions to a certain extent, hindering the compactness of the pellets and the growth of the grains

Using conventional direct addition of Cr 2 o 3 、Al 2 o 3 Such sintering aids can improve the sintering activity of the powder, but may react with BeO, affecting the thermal conductivity and distribution of the BeO phase, which is not conducive to the improvement of the thermal conductivity of the pellet

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